Talk Composites - The Forum for Advanced Composites

Repairing damaged carbon fibre car doors

http://www.talkcomposites.com/Topic8616.aspx

By RyanParle - 11/25/2013 4:14:39 PM

A few years ago i bought some carbon fibre doors for my classic mini from a fairly well known supplier and on unpacking them i discovered that they were both damaged, there is a linear fracture about 2" long on one and a "spider" fracture on the other about 2" x 3"from what i can see the fractures are in the resin and the fibre beneath looks intact. The supplier refused to replace them or repair them, i said i would pay for the repair if he aranged them to be collected from me by courier, the supplier agreed, but never sent a collection despite many phone calls. in the end i decided that i would live with the damage.

since then i got them fitted which turned out to be a much harder job than it should have been as they turned out to be a bit thicker than the original steel doors and would foul on the body work and then after a few weeks exposure to the elements they also started to discolour (even though i was assured that they wouldn't!

After taking on my first carbon fibre project of making a fog light pod using the wet lay technique I decided that i would have a go at repairing the doors, but i am not sure how to go about it.

I originally though about carefully sanding back the gel coat / resin and then spraying on a new coat and flatting / polishing them up to a smooth finish, but i am unsure if this will remove all of the discolouration or if there will still be some discoloured resin in the weave of the carbon. Is this a viable method to repair the cracked resin and remove the discolouration?

Then on the weekend i was looking at the way the doors are assembled and realised that the extra thickness comes from the way the inner and outer sections are bonded together, the join has about 8mm of "bonding material"  which looks like it is resin and a bit of loose fibre re-enforcement,  between the two sections. I feel that the two sections could have been bonded in a better way (for example the way demonstrated in the tutorial videos on here) so i am now considering taking a mould from the existing door skins and making new skins myself. then i can remove the original skins, clean up the inner frames and make a neater job of bonding the two sections together.

Any thoughts on this would be much appreciated. 

Obviously if i go down the route of making new door skins i would choose to use the resin infusion method in order to achieve the best results possible, so it will cost a fair bit more to do, however i am also in the process of designing a new dashboard so that i can get the instrumentation & switches mounted in a place where it can all be seen / operated whilst harnessed in, so at some point buying the resin infusion kit will be required.
By andygtt - 11/28/2013 3:21:32 PM

Im pretty sure there isn't a UV stable epoxy resin so that was a mistake from the supplier... you could sand back the top coat of the resin and clear coat it assuming its not too badly discoloured.

What I would do is take moulds and make my own... then sell the existing doors to fund it. but its a lot of work.

When I bonded my carbon doors together I had around 1-3mm of bonding filler between the panels at most... if you use the correct materials you don't need loads of material between them. The correct materials are more expensive however which is probably why they did it the way you describe... cutting them apart and bonding them closer shouldn't be that hard especially if you do go the clear coat route.